Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
The invention relates generally to fastener drive
tools, and more particularly to anvil-type or hammer drive,
powder actuated tools.
Many types of fastener drive tools and like explosively
actuated equipment have been developed over the years, and such
tools have had complex mechanisms for firing pin operation, for
ejecting or extracting spent cartridge shells and for meeting
safety standards. Recent developmental trends are toward improved
low velocity tools of the type in which a piston ram member
is explosively driven to actuate a nail or like fastener into a
workpiece such as concrete or wood. One type of low velocity
tool is described in U. S. Patent No. 3,066,302, which tool uses
a pistol-type firing pin mechanism having a trigger and sear to
trip a spring-loaded firing pin that is cocked by compressing the
muzzle end of the tool telescopically rearwardly within the tool
housing. Many such pistol-type low velocity tools are disclosed
in the prior art.
Another type of low velocity tool is described in U. S.
20 Patent No. 4,025,029, which tool, like the present invention,
is a hammer-activated, powder actuated stud driver. Such hammer
drive tools are conventionally operated by placing the muzzle end
of the tool against the workpiece and striking the rear end of
the tool with a hammer to fire the cartridge or like powder
charge. Hammer drive tools heretofore, while simple in con-
struction and operation, have been inherently dangerous due to
the fact that a loaded tool could be fired if accidentally
dropped. U. S. Patent No. 3,688,964 discloses another low
velocity hammer drive tool designed for caseless loads and having
some safety features.
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SUMMARY OF THE INVENTION
The present invention comprises a low velocity, powder
actuated tool of the type utilized in construction and other
trades, and particularly adapted for use in the home, shop or the
like by semi-skilled persons.
The principal object of the present invention is to
provide a novel fastener drive tool of the hammer drive or
impact type; one that is cf simple, rugged construction and
eliminates the complex and expensive forms of closure, trigger,
sear, firing pin, cartridge holding and ejection and like
mechanisms of prevalent tool design.
Another object is to provide a powder actuated tool
that is highly efficient in operation and provides exceptional
safety standards against drop-fire and other accidental tool
discharge incidents. A more specific objective is to provide
triple safety means requiring positive manual operation as well
as substantial striking force to accomplish firing actuation of
the tool.
Still another object is to provide a hammer drive tool
that meets the three safety requirements of the American
National Safety Code.
These and still other objects and advantages will
become more apparent hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings which illustrate embodiments of the
invention,
FIGURE 1 is a longitudinal cross-sectional view of a
hammer drive, powder actuated tool in the expanded or loading
position thereof;
FIGURE 2 is a longitudinal cross-sectional view
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of the tool in its compressed condition at the instant of powder
detonation;
FIGURE 3 is an enlarged fragmentary cross-sectional
view taken substantially along line 3-3 of FI~URE l;
FIGURE 4 is an enlarged fragmentary cross-sectional
view taken substantially along line 4-4 of FIGURE 2, but being
rota~ed 90 for correct depiction; and
FIGURE 5 is an enlarged fragmentary cross-sectional
view taken substantially along line 5-5 of FIGURE 1, but being
rotated 90 for correct depiction.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings wherein the hammer drive,
powder actuated tool 10 is illustrated as a presently preferred
embodiment of the present invention, the tool 10 comprises a main
cylindrical housing member 11 having a rear firing pin bore
section 12 and a front barrel bore section 13 with an intermediate
breech or loading area 14. A primary solid anvil member 17 is
rigidly secured in the firing pin bore 12 of the main housing 11
by a cross pin 18, and a "floating" firing pin assembly 19 is
housed in the firing pin section 12 between the primary
anvil mass 17 and the breech or loading area 14, as will be
defined more fully hereinafter. A safety lever assembly 20 is
pivotally mounted on the main housing 11 intermediate to the
firing pin section 12 and breech area 14, and one of its purposes
is to limit or restrict free floating forward movement of the
firing pin assembly 19 toward the breech section 13. The main
housing 11 has a lateral breech opening ~1 for access to the
inner breech or loading area 14 for purposes of cartridge ejec-
tion and reloading of the tool 10. The main housing 11 is
provided with a two-piece outer resilient hand grip or
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housing covering 22 which circumscribes the rear firing pin
section 12 and is associated with the safety lever assembly 20,
as will be described.
A barrel ram guide member 23 is slidably mounted in the
front barrel section 13 of the main housing 11, the guide member
having a bore 24 in which a barrel extension 25 is threadedly
engaged at the muzzle end. The barrel extension 25 has a bore 26
concentric with the ram guide bore 24 and an annular shoulder 27
is formed between the bores 24 and 26. The ram guide 23 also has
a breech plug 28 threadedly engaging the breech end of the
bore 24, the breech plug 28 having an ignition cavity 29 for
receiving a powder cartridge C (see Fig. 1) or like powder charge.
A ram or piston member 30 has an enlarged head 31 with a close
tolerance sliding fit in the ram guide bore 24, and an axially
extending cylindrical ram or piston rod 32 is slidably positioned
in the barrel extension bore 26 with a free or working end
therein for engagement with a fastener F. The ram head member 31
has an annular steel or like O-ring seal 35, and an annular
abutment sh~ulder 36 on the head member 31 defines the end of the
recess between the piston rod 32 and the ram guide bore 24.
The ram and ram guide members 30 and 23 comprise fastener drive
means for orienting the ~astener member F in the tool 10 and for
driving such fastener F into a wor~piece (not shown) in a con-
ventional manner readily apparent to those skilled in the art.
The ram head 31 is also provided with an axially extending
ejection pin 37 for dislodging spent cartridge shells C from the
gnition cavity 29.
An important feature of the tool 10 comprises frictional
abutment means 38 adjacent to the muzzle end of the main barrel
housing 11. The ram guide member 23 has a longitudinal slot 39
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extending a major portion of the guide member length, and an
arcuate transverse slot 40 is formed in the main housing wall 11
to thereby accommodate a spring clip 41 forming part of the
frictional abutment means 38, see FIGURES 1 and 3. The spring
clip 41 has a U-shaped central body 42 extending radially inwardly
through the ram guide slot 39 into the recess for abutment by the
ram head shoulder 36, and arcuate friction wings 43 are formed as
outward re-entrant curves from the opposed walls of this central
body 42, FIGURE 3. The frictional abutment means 38 also includes
a spring steel retainer band 45 having an inner end flange
46 received between the spaced walls of the spring clip central
body 42 to maintain the band 45 in circumscribing relationship
around the muzzle end of the main housing 11.
Referring to FIGURE 2, the tool 10 is shown in its
fully compressed diring position with the ram 30 and ram guide 23
being retracted in telescopic relation within the main housing 11
and the firing pin assembly being compressed in the condition of
the tool 10 at the precise instant that a hammer driven force is
applied to the primary anvil member 17 to detonate the powder
charge C in the breech plug 29. It will be understood by
those skilled in the art that the force exerted upon the ram head
31 drives the ram 30 axially in the ram guide 23 and barrel
extension 25 so that the working end 33 drives the fastener F
from the muzzle end of the barrel extension 25 into the workpiece
(not shown). Thus, whe~ the tool has been fired, the ram 30 will
naturally be positioned in the ram guide 23 leftwardly of the
position shown in FIGURE~ 1 and 2 until the piston guide is also
moved leftwardly (as in FIGURE 1) to its expanded, re-loading
position. This action is carried out by snapping the muzzle
end of the tool outwardly in a swinging movement to throw
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the ram guide outwardly in the main housing bore 13 against the
frictional force exerted therebetween by the spring clip wings 43
of the spring clip 41. In this movement the ram guide 23 moves
to its fully extended loading position with the frictional
abutment means 38 engaging the end of slot 39, and the ram 30 is
also engaged with its abutment shoulder 36 against the U-shaped
central body 42 of the spring clip. Thus, in the FIGURE 1 position
of the tool 10, the ejection pin 37 projects into the cartridge
or ignition cavity 29 of the breech plug 28 to eject the spent
cartridge shell, which is dropped through the breech opening
21 by inverting the tool 10 from its FIGURE 1 position. It will
be readily apparent that the frictional abutment means 38 return
the ram and ram guide members 30 and 23 to their loadir,g relation-
ship for inserting a new fastener F in the muzzle end of the
barrel extension 25 and a cartridge C in the ignition cavity 29
of the breech plug 28. The frictional abutment means 38 also
prevents relative rotation of the ram guide member 23 in the main
housing 11, and the spring clip 41 and retainer band 45 act
frictionally between the ram guide member 23 and main housing 11
to maintain the ram guide frictionally in any adjusted axial
position. The steel friction spring 35 between the ram head 31
and ram guide bore 24 maintains the adjusted axial position of
the ram 30 in the ram guide member 23.
Referring particularly to FIGURES 1, 4 and 5, the
firing pin mechanism of the tool 10 includes the primary anvil
mem~er 17 having a centrally projecting impact or anvil block 49
with s~riking face 50, and a strong drop-spring 51 is positioned
on the anvil block 49 and extends concentrically forwardly in the
firing pin bore 12 to oppose movement of the ram guide 23 and
its cartridge carrying breech plug 28 toward firing position.
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The spring 51 has a substantial force of approximately 25 to
35 ft. lbs., which is several times the weight of the tool and
thereby forms a first safety mechanism to substantially obviate
drop-fire incidents. The "floating" firing pin assembly 19
includes a secondary anvil mass or plug 52 slidably positioned in
the firing pin bore section 12 of the main housing 11, and a
circular firing pin 53 is integrally formed on its forward face
in the breech area 14 and is axially aligned with the ignition
chamber 29 of the ram guide member 23. The secondary anvil and
firing pin member 52,53 is biased forwardly toward the
breech area 14 by the strong or "heavy" drop-spring 51, but a
stop key or pin 54 projects radially from the secondary anvil
member 52 and is guided in a longitudinal slot 55 in the main
housing wall 12 to limit forward movement of the firing pin
assembly 19 toward the breech area 14.
The firing pin assembly 19 also includes secondary
safety means associated with the secondary anvil 52. The anvil
52 is bored through, at 56, on opposite sides of the firing pin
53 and is counterbore from the back, at 57, and receives a pair
of diametrally disposed headed studs or safety rivets 58.
The rivets 58 are biased by firing pin safety springs 61 positioned
in the counterbore 57 and retained therein by a tempered closure
anvil block or plate 62, which is welded to the back surface of
the anvil plug 52 and serves to retain the forward end of the
drop-spring 51. The secondary anvil m~mber 52 also has a for-
wardly projecting annular shoulder 63 at its periphery, which is
adapted to interfit with an annular peripheral recess 64 in the
breech plug 28 ther~by forming a sealing arrangement at the point
of firing contact of the firing pin 53 with a cartridge C. It
may be noted that the firing pin 53 has a complete centerfire
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fit with the percussion flange of the cartridge C, and firing
indentation of the cartridge C by penetration of the firing pin is
controlled by the sealing arrangement. The safety stud springs
61 are also of substantial force or "heavy", each being about the
same magnitude as the drop-spring 51 (approximately 28 ft. lbs.)
whereby the combined spring forces to be overcome to fire the
tool 10 substantially eliminate accidental firing incidents.
The safety lever assembly 20 comprises the third safety
device of the present tool 10, and comprises an elongated
lever body 66 longitudinally disposed along the firing pin
section 12 of the housing 11 and contained within the cavity
section 65 formed in the resilient covering 22 therefor. A
safety latch or lug 67 is formed substantially at right angles on
the forward end of the lever body 66 and extends radially inwardly
of the cylindrical main housing 11 through a transverse slot 68
and defines the forwardmost limit of the firing pin assembly 19
as a secondary stop to the limit plug 54. More importantly, the
latch 67 acts to prevent accidental rearward movement of the ram
guide member 23 as will be described. The other end of the lever
body 66 is provided with a handle 70 extending outwardly of
the resilient covering 22, and the lever body 66 is hinged or
pivoted on the main housing 11 on a fulcrum mounting lug 69
intermediate to the latch 67 and the outwardly extending handle
portion 70. A wrap-around spring 71 or the like compresses the
latch member 67 inwardly to form the safety abutment in the main
housing bore, and the spring 71 is overcome by depressing the
handle 70 radially inwardly against the hand grip covering 22.
It will be apparent that the handle-fulcrum-latch relationship
can be modified to provide optimum safety lever action.
In the extended, loading position of the tool 10
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as shown in FIGURE 1, a new cartridge C is inserted into the
ignition cavity 29 thereby pressing against the ejection plug 37
and axially moving the entire ram 30 slightly to the left, where
the ram 30 is held in position with the ram guide 23 by the
friction sealing spring 35. A fastener F is inserted in the
muzzle end of barrel extension bore 26 against the ram work face
33, and the fastener drive and guide means 30,23 is moved rear-
wardly toward the firing pin section 13 to close the breech
opening 21 and position the breech plug 28 of the ram guide 23
against the ends of the safety guide rivets or studs 58,
which project axially beyond the safety lever latch 68, FIGURE 1.
Although the safety lever mechanism 20 forms the only positive
interference safety device, that prevents unrestricted axial
movement of the guide means 23 and firing pin assembly 19
into contacting or firing abutment, the combined force of the two
firing pin safety springs is approximately 56 ft. lbs. and
effectively prevents compressive firing action by the operator or
other inadvertent compressive forces of great magnitude, such as
accidental drop-fire incidents. Therefore, it will be seen that
in the normal sequence of compression, the drop-spring 51
would first become compressed to bring the ram guide 23 into
abutment with the safety latch 68 before the firing pin safety
springs 61 will give way to striking engagement between the
firing pin 53 and cartridge C in the breech plug 28.
In actual operation, when the tool 10 is positioned
against a workpiece (not shown) and ready for firing, the ram and
ram guide 30,23 will be telescoped into the barrel housing with
the breech plug 28 abutting the ends of the safety rivets 58.
The safety lever handle 70 is then depressed to pivot the latch
68 out of the barrel bore 14 against the action of spring
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71, and the primary anvil 17 is struck solidly by a heavy hammer
(not shown~ weighing about one pound or greater. It is again
emphasized that the hammer force must overcome the 25 to 30 ft.
lbs. force of the spring 51 to drive the primary and secondary
anvil members 17 and 52,62 together and also overcome the combined
forces of firing pin safety springs 61 to provide firing contact
of the firing pin 53 against the cartridge C, as shown in FIGURE 2.
It will thus be readily apparent that the two firing
pin safety studs 58 and springs 61, as positioned immediately
adjacent to the firing pin 53 and acting in opposition to
relative firing actuation, assure the deliberate and safe operation
of the tool 10 and assure against substantially all inadvertent
tool mishaps. From the foregoing description it will be readily
apparent that the present fastener drive tool 10 meets the
various objectives of simplicity, safety and efficiency in
construction, handling and operation. The essential simpli-
fication of the invention pertains to the "floating" secondary
anvil 52 that is spring loaded by a "heavy" spring 51 away from
the primary anvil mass 17, and in the provision of a positive
safety latch 20 that is manually retractable to condition
the tool for firing. It may be noted that the handle 70 of the
safety lever 20 is positioned radially inwardly of the large end
flange of the resilient hand grip 22 so that it is also protected
against release due to accidental dropping incidents. Various
changes and modifications of the tool 10 will be apparent to
those skilled in the art without departing from the inventive
concept. Accordingly, the invention is limited only by the scope
of the claims which follow.
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